This is a competitive supplement (CS) application to the existing R01, titled "Follow-Up of Vietnam Veterans at Risk for Suicide"(MH060961), hereafter referred to as the Parent Grant (PG). Additional support is requested for the remaining 17 months of the Parent Grant to conduct detailed examination of chronic post-traumatic stress disorder (PTSD). More than two decades have passed since PTSD was officially incorporated into the Diagnostic and Statistical Manual (DSM)-in. However, given the relative "newness" of PTSD as a psychiatric diagnosis, research on chronic PTSD has traditionally used retrospective information from small numbers of survivors obtained many years after the original trauma. The field is reaching a prime time in the U.S. because Vietnam veterans are the largest clearly-definable surviving population at risk for chronic PTSD, currently representing 8.5% of U.S. adult males, for whom the history of PTSD dates back as long as 30 years. While the PG aims relate to the mechanisms of coping and other protective factors mitigating suicidal risk, the CS focuses on chronic PTSD by utilizing an already implemented assessment of phenomenology, triggers and event linking of PTSD symptoms, and the longitudinal data accumulated from this cohort since 1972. The PTSD assessment was added to the PG after September 11, 2001. The specific aims of this twice-revised application include: 1) Validity: examine the consistency of the standard assessment of PTSD symptoms conditioned on a specific single trauma with the PTSD symptoms that are differentially attributed to multiple traumas; 2) Qualitative: examine the phenomenology of chronic PTSD, including types of traumatic events, description and triggers of symptoms, and attribution of symptoms to traumatic events; 3) Quantitative: disentangle multiple pathways to chronic PTSD, including vulnerability and comorbidity, "kindling" or "stoking" effects of traumatic events, and symptom "compilation," using both person-based and traumatic event-based data; 4) Qualitative-quantitative integration: examine the association of multiple pathways to chronic PTSD with the current PTSD symptomatology and trauma attribution; and 5) Examine the "inoculation" vs. "exacerbation" hypothesis for the effect of traumatic events on chronic PTSD by utilizing September 11 as a "natural experiment." An estimated 420 Vietnam veterans will comprise the effective analysis sample, including three groups of "suicide high-risk" (n~135), "suicide low risk" (n" 215) and "suicide medium-risk with PTSD" (minimum n=66) who will be newly added to the CS to include DSMITJR [unreadable] PTSD positives not selected in the PG. Lifetime prevalence of DSM-FV PTSD in the total CS sample is 33.4% (62.2%, 0.8%, and 66.7% for the three groups, respectively); 89% of the positives had active PTSD during the past 5 years prior to the last assessment in 1996-7. We hope the new findings will increase the understanding of the complexity involved in chronic PTSD and provide insights to improve treatment for this Vietnam veteran and other populations of PTSD sufferers. [unreadable] [unreadable]